The calculation capacities and information communication capabilities of computers have improved, prompting demand for dramatically higher performance of external information storage devices in recent years. In particular, there is a growing demand for a hard disk drive capable of high density recording of over 1 Tb/inch2. However, with the record surface density of 1 Tb/inch2, the size corresponding to one bit is approximately 25 nm square or the like, and the size corresponding to each record bit is extremely small. For this reason, detection of recorded information is expected to be difficult with an element of a known spin valve scheme such as a GMR (Giant Magneto Resistance) element or a TMR (Tunnel Magneto Resistance) element. Under such circumstances, there is a demand for an element for achieving the required standard of the 1 Tb/inch2, based on a detection principle that are distinct over the known principle.
As a new detection principle different from the known ones, there is Aharonov-Bohm (AB) effect which is described in the below-listed non-patent document 1. This is an effect that, when electron waves propagate while maintaining coherency thereof, the phase difference of the two electron waves is affected by a vector potential formed by a magnetic flux penetrating a space between the paths of the two electron waves. This will be hereinafter described again with further detail. Further, patent document 1 discloses a magnetic field detector utilizing the AB effect and the coherency of the electrons. Further, the below-listed non-patent document 2 reports that, even without the presence of a magnetic field, phases of electron waves vary with application of an electric field inside a substance due to spin orbital interaction of the substance (Aharonov-Casher (AC) effect; see non-patent document 3 for more detail of this effect). In a known magnetism detecting element, it is necessary to temporarily transfer a magnetic field onto a soft magnetism layer, prior to detecting variation in a magnet resistance. On the other hand, in an electromagnetic field detecting element utilizing AB effect or AC effect as a detection principle, the target to be detected is a vector potential and not an electromagnetic field, and therefore does not require the transferring process. Therefore, no attenuation or delay attributed to the transfer process will take place. This is advantageous in that a highly efficient electromagnetic field detection is possible, and reproducing of extremely small magnetic bits is possible.    [Patent document 1] Japanese Unexamined Patent Publication No. 306412/1990 (Tokukaihei 2-306412)    [Non-patent document 1] Hidetoshi FUKUYAMA, “Series Bussei Butsuri no Shintenkai, Mesoscopic kei no Butsuri”, P. 55 to 57, Published in 1996 by MARUZEN Kabushiki kaisya, Publishing dept.    [Non-patent document 2] “NATURE VOL. 427”, P. 50 to 53, Published in January, 2004    [Non-patent document 3] “Physical Review Letters Vol. 53”, P. 319 to 321, Published in July 1984